The quadriceps were taken near the end of the pipeline, roughly 6–10 minutes after completion of perfusion. Quadriceps were collected by cutting evenly across the upper axis of the femoral bone. Quadriceps muscle lying below or beside this femoral axis was not taken. The quadriceps was then placed in liquid nitrogen. At a later date, quadriceps were retrieved from -80 storage and shattered in liquid nitrogen. Roughly ~100 mg fragments were taken at random for mRNA preparation for every individual. To account potential differences in the tissue taken (as the tissue was not pulverized into powder), all ~5 animals per cohort had their RNA prepared, and then were pooled evenly (by µg of RNA) into a single RNA sample for each cohort. These pooled RNA samples of approximately 30 µg RNA were then purified using RNEasy, then sent out for array analysis. All RIN values were > 8.0. 

Tissue preparation was done in two different steps: the first half of the cohorts were run in October 2011, while the second half was run in August 2012. This tissue was the first microarray run at this platform, and thus the quadriceps served as a pilot to ensure that data quality would be good. The first half of the cohorts are: CD: C57, DBA, 44, 45, 51, 55, 61, 62, 63, 66, 70, 73, 75, 80, 83, 87, 89, 90, 96. HFD: C57, DBA, 44, 45, 51, 55, 61, 62, 63, 66, 70, 73, 75, 80, 83, 87, 90, 96, 100. The second half of the cohorts were the remainder. The preparation of all samples was done by the same technician with the same technique, other than the year time differential